The 200 metres freestyler won the first of Scotland's nine gold medals in Delhi but the subsequent flood of accolades and recognition would prove fleeting. On the few occasions the 26-year-old swimmer is recognised these days, as he does his weekly shopping or goes to the cinema, it tends to be by those with an interest in his chosen sport.
"It happens sometimes and I usually end up talking to them for five or 10 minutes about swimming, so that's no problem," he says quite cheerfully.
Renwick, who will look to defend his 200m title in Glasgow while also competing in the 400m freestyle and three relay events, does not expect to remain a high-profile figure regardless of what he achieves at these Games, well aware that it takes something special to muscle in on the nation's obsession with football - and footballers - to the detriment of just about everything else.
Renwick has no problem with that but when he sees the kinds of vacuous characters given a public platform in this country - the reality television stars and their ilk - it does make him wonder why professional athletes are not used more often as positive role models.
Swimmers, after all, put in hour after hour of unstinting devotion to their discipline, make personal sacrifices to further their careers, look after themselves physically, and rarely do anything away from the pool to tarnish their reputations.
"My life is pretty simple. I train first thing in the morning, during the day and in the evening," he added. "When I'm not training I'm recovering, so I don't really come across the general public too much. I don't think many of them know who I am, which probably helps. It's nice to be recognised for your achievements, but generally I keep myself to myself.
"I feel, though, we're the ones that people should be looking up to, not the glamour models or the reality TV shows. We're the ones that the young generation need to look at so that they can be the stars of the future. But a sport like swimming doesn't get huge audiences like football, which is understandable."
Not all athletes are entirely wholesome individuals, of course. The spectre of doping is never too far away from professional sport, and swimming is no different in that regard. Renwick is not as vehement on the matter as team-mate Michael Jamieson but acknowledged it is a problem that is not going away.
"I'm not really an expert on doping, but it's an unfortunate reality that it happens in sport and it happens in swimming. It's a shame. I can't imagine why you would ever do it. I hope the ones who choose to go down that route get caught and get a long ban."
Renwick believes he would only be torturing himself were he to start to question whether all his rivals were competing fairly or not. "I choose to believe that everyone I race against is clean. I wouldn't like to think all the time 'Oh, he's really good - he must be cheating'.
"I don't think anyone can accuse the Scottish team of that. I don't feel like we're at that level yet to be accused of doping. If you look at the Americans and the Chinese winning all the gold medals, then get some people pointing fingers at them. We're a small nation. We punch well above our weight. You just look at the quality of swimmers we've got - I don't think you can accuse us of doping."
The escalation of social media platforms has drastically shrunk the distance between public figures and their public. Renwick is usually a keen conversant with his 11,500 Twitter followers but has decided to detach himself during the period of the Games, lest it become an unnecessary distraction.
"I've taken Twitter and Facebook off my phone for the last couple of months," he revealed. "Straight away it was a huge relief. I was constantly refreshing this thing [his phone] and I just thought to myself one day 'What am I doing? I'm wasting my life away on this thing'.
"The novelty had worn off for me. It's stuff other people say that winds me up and I want to get involved in that conversation and then I'm like 'Look, don't get involved, just take a step back'. So for me it was best to just get rid of it all. I'm sure after the Games I'll be back on it."